OBJECTIVE: To draw attention to primary hyperparathyroidism as a cause of severe hypertension. RESULTS: A 47 year old Nigerian male presented with headache, occasional blurring of vision and dyspnoea on mild exertion of 2/12 duration. He had been troubled by painful osteoarthritis of the knees for 2 years for which he was taking NSAIDs. He was found to be severely hypertensive, BP 210/130mmHg and had bilateral knee crepitus. BP was resistant to control on Nifedipine R and Moduretic. Serum urea, creatinine, uric acid were normal but there was hyperacalcaemia and hyperchloraemia. Haematological indices, urinalysis, microscopy and culture of urine were normal. Parathyroid hormone level was raised. A parathyroid MIBI scan study showed an extensive area of significance towards the inferior pole of the right lobe of thyroid medially with a second area of very low significance medial to the left pole. These findings indicated the presence of a right inferior parathyroid adenoma. He had parathyroid surgery and a large adenoma in the right inferior gland and a smaller left inferior gland were removed and confirmed histologically. Corrected calcium and parathyroid hormone levels dropped to normal, and the BP was easily controlled with Lisinopril 5mg daily subsequently. He is not currently on antihypertensive medication two years post surgery. CONCLUSION: This case highlights the need for thorough investigation of cases of hypertension to exclude specifically secondary causes, which in some cases may be endocrine in origin and may easily be corrected.